In recent years, metal oxide semiconductor (MOS) solid-state imaging devices are being mounted in mobile device cameras, in-vehicle cameras, surveillance cameras, and so on.
High-resolution imaging performance is required from such solid-state devices, and miniaturization and higher pixel count are necessary for the solid-state imaging devices. In conventional solid-state imaging devices, the size of a photodiode is also reduced due to pixel miniaturization. With this, there is the problem that sensitivity deteriorates due to a deterioration in saturation signal level and reduced aperture ratio.
A layered solid-state imaging device has been proposed as a solid-state imaging device for solving this problem. In the layered solid-state imaging device, a photoelectric conversion film is stacked on the top surface of a semiconductor substrate. Furthermore, light enters from above the stacked film. In addition, the solid-state imaging device has a structure in which the charge generated in the photoelectric conversion film by photoelectric conversion is read out using a charge coupled device (CCD) circuit or a complementary MOS (CMOS) circuit.
Patent Literature (PTL) 1 describes a conventional layered solid-state imaging device. FIG. 6 is a circuit diagram of a pixel circuit of the solid-state imaging device described in PTL 1. In the pixel circuit illustrated in FIG. 6, a charge accumulation region (FD) and a pixel electrode 15a are electrically connected, and the voltage of the charge accumulation region varies according to the intensity of incident light. Furthermore, the charge accumulation region is also electrically connected to the gate electrode of an amplification transistor 17b. Therefore, with this pixel circuit, it is possible to amplify the amount of voltage change in the charge accumulation region and read out the resulting voltage to the signal line 17d. 
In the above-described layered solid-state imaging device, the photoelectric conversion film is formed stacked on the upper portion of a wiring layer used in a read-out circuit and a signal processing circuit, but the charge obtained through photoelectric conversion is accumulated in the charge accumulation region provided in the semiconductor substrate. As such, the charge obtained through the photoelectric conversion is transmitted to the charge accumulation region via a metal plug.